High-performance cross-linked cationic concrete air entraining agent and preparation method thereof

Abstract

The invention relates to the technical field of concrete admixtures, in particular to a high-performance cross-linked cationic concrete air entraining agent and a preparation method thereof. The preparation process of the air entraining agent comprises the following steps: under the protection of inert atmosphere, carrying out reflux reaction on a polyamine compound and brominated alkane, and then mixing and emulsifying with an emulsifier and a sodium citrate solution to obtain pre-emulsified liquid; mixing the pre-emulsion with hydrophilic polyoxyethylene ether, an initiator and a phosphate modifier, and carrying out initiation cross-linking reaction by adopting ultraviolet irradiation to obtain an intermediate product; mixing and stirring the intermediate product with a micro-nano bubble solution, pretreated nano cellulose and a foam stabilizer, and then performing reduced pressure distillation and filtration to obtain an air entraining agent; a highly uniform and stable micro-nano bubble system is formed in the concrete, the air entraining agent can significantly improve the freeze-thaw cycle resistance, mechanical strength and durability of the concrete, and the preparation process is mild in condition and environmentally friendly.

Description

Technical Field

[0001] This application relates to the field of concrete admixture technology, specifically to a high-performance cross-linked cationic concrete air-entraining agent and its preparation method. Background Technology

[0002] Concrete, as a core material in modern construction, is crucial for its durability and workability. Air-entraining agents are key admixtures that significantly improve concrete's freeze-thaw resistance, impermeability, and workability by introducing a large number of uniform, closed micro-bubbles into the concrete.

[0003] However, traditional air-entraining agents generally suffer from poor bubble stability and insufficient compatibility with cement paste, limiting their performance in harsh environments or high-strength concrete applications. Currently, the main products in the concrete admixture market include traditional air-entraining agents such as rosin resins and alkylbenzene sulfonates. However, existing anionic air-entraining agents are more sensitive and easily deactivated in high-salt and alkaline concrete environments, while nonionic air-entraining agents require large dosages and have poor bubble stability, resulting in decreased compressive strength of the concrete. Current air-entraining agents have failed to solve the problem of long-term stability in complex concrete systems, leading to insufficient concrete durability.

[0004] Developing high-performance concrete air-entraining agents that exhibit stable and persistent bubbles, good compatibility with cement paste, and adaptability to harsh working conditions is of significant value and importance. Furthermore, with the advancement of environmental protection policies and the increasing demand for solid waste resource utilization, the concrete air-entraining agent manufacturing industry also needs to develop innovative materials that combine high performance with ecological benefits. Therefore, developing a high-performance concrete air-entraining agent with a mild preparation process, efficient solid waste resource utilization, stable and persistent bubbles, and good environmental compatibility has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] This application aims to overcome the above-mentioned deficiencies of the prior art and provide a high-performance cross-linked cationic concrete air-entraining agent and its preparation method, the technical solution of which is as follows: The method for preparing the high-performance cross-linked cationic concrete air-entraining agent provided in this application includes the following steps: S1. Under an inert atmosphere, polyamine compounds and bromoalkanes are refluxed in an organic solvent. The resulting reaction solution is then mixed with an emulsifier and sodium citrate solution, dispersed, and then heated to emulsify, resulting in a homogeneous pre-emulsion. S2. The pre-emulsion is mixed with hydrophilic polyoxyethylene ether, initiator and phosphate ester modifier. Under deoxygenation and temperature control conditions, ultraviolet light is used to initiate the polymerization and cross-linking reaction of the system to obtain the intermediate product. S3. The intermediate product is mixed and stirred with the micro / nano bubble solution, pretreated nanocellulose and foam stabilizer, and then the volatile unreacted monomer components are removed by vacuum distillation. Finally, the mixture is filtered to obtain the air-entraining agent. The pretreated nanocellulose is obtained by modifying nanocellulose with a silane coupling agent.

[0006] In some embodiments, S1, under an inert atmosphere, the polyamine compound and the bromoalkanes are refluxed in an organic solvent at 60-70°C for 2-4 days. The resulting reaction solution is then mixed with an emulsifier and a sodium citrate solution, and after ultrasonic dispersion, the mixture is heated to 60-80°C and stirred for 1-3 hours to emulsify, thereby obtaining a homogeneous pre-emulsion. The reactant components, by weight, include: 2-5 parts of polyamine compound, 10-12 parts of bromoalkanes, 40-50 parts of organic solvent, 1-2 parts of sodium citrate solution, and 5-8 parts of emulsifier.

[0007] In some embodiments, the polyamine compound is one or more of N-(3-aminopropyl)-1,3-propanediamine, N,N'-methylenebisacrylamide, 1,1,4,7,10,10-hexamethyltriethylenetetramine, N,N,N',N'-tetramethylethylenediamine, and 1,1,4,7,7-pentamethyldiethylenetriamine.

[0008] In some embodiments, the bromoalkane is one or more of 1-bromooctadecane, 1-bromopentadecanane, 1,14-dibromotetradecane, 1-bromotetradecane, and 1-bromododecane.

[0009] In some embodiments, the emulsifier is one or more of sodium stearate, sodium dodecyl sulfate, benzalkonium chloride, and polysorbate-80.

[0010] In some embodiments, the organic solvent is tetrahydrofuran.

[0011] In some embodiments, the concentration of the sodium citrate solution is 1%–2%.

[0012] In some embodiments, S2, a portion of the pre-emulsion is mixed with hydrophilic polyoxyethylene ether, initiator and phosphate modifier, oxygen in the reaction environment is removed by passing an inert gas, and the temperature of the reaction system is controlled at 23-27°C. Under constant temperature conditions, the mixture is irradiated with ultraviolet light at a wavelength of 365nm for 3-5 hours to obtain an intermediate product; wherein, by weight, the reaction raw material components of S2 include: 20-25 parts of pre-emulsion, 15-20 parts of hydrophilic polyoxyethylene ether, 1-2 parts of initiator, and 10-15 parts of phosphate modifier. In some embodiments, S3, the micro / nano bubble solution, the pretreated nanocellulose suspension, and the foam stabilizer are added to the intermediate product and stirred until homogeneous. Then, the volatile unreacted monomer components are removed by rotary evaporation under reduced pressure at 40°C-60°C, and finally filtered to obtain the air-entraining agent. The reaction raw material components of S3, by weight, include: 10-15 parts of micro / nano bubble solution, 8-10 parts of pretreated nanocellulose suspension, and 1-5 parts of foam stabilizer.

[0013] In some embodiments, in step S3, the stirring and mixing time is 30-50 minutes; the filtration is performed using a microporous membrane with a pore size of 0.22 μm.

[0014] In some embodiments, the hydrophilic polyoxyethylene ether is one or more of polyoxyethylene oleyl alcohol ether, polyoxyethylene lauryl alcohol ether, polyoxyethylene fatty alcohol ether, and polyoxyethylene alkylphenol ether.

[0015] In some embodiments, the initiator is one or more of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, dodecyl peroxide, potassium persulfate, and ammonium persulfate.

[0016] In some embodiments, the phosphate modifier is one or more of triisopropylphenyl phosphate, phosphate acrylate, tris(2,4-di-tert-butylphenyl) phosphate, potassium 2-(m-tolyloxy)ethyl phosphate, and hydroxyethyl methacrylate phosphate.

[0017] In some embodiments, the foam stabilizer is one or more of dodecyl dimethylamine oxide, alkanolamide, polyethylene glycol, polyvinylpyrrolidone, and coconut oil diethanolamide.

[0018] In some embodiments, a microbubble generating device is used to treat water to generate a micro / nanobubble solution, wherein the bubble size distribution is 0.1 μm-50 μm and the bubble concentration is 10. 7 Cells / mL–10 8 cells / mL; In some embodiments, the pretreated nanocellulose is obtained by surface modification reaction of nanocellulose with a silane coupling agent in an alcohol solution, followed by solid-liquid separation and washing.

[0019] In some embodiments, the preparation process of the pretreated nanocellulose suspension is as follows: nanocellulose is mixed evenly with an alcohol solution, then a silane coupling agent is added, the mixture is stirred at room temperature for 2-4 hours, centrifuged and filtered to separate the components, and washed with an alcohol solution to remove unreacted coupling agent, thus obtaining the solution; wherein, by weight, the raw material components include: 10-15 parts nanocellulose, 100-150 parts alcohol solution, and 1-3 parts silane coupling agent.

[0020] In some embodiments, the silane coupling agent is one or more of γ-(methacryloyloxy)propyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, octadecyldimethyltrimethoxysilylpropylammonium chloride, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and bis-(γ-triethoxysilylpropyl)tetrasulfide.

[0021] In some embodiments, the alcohol solution is an ethanol solution.

[0022] This application provides a high-performance cross-linked cationic concrete air-entraining agent, which is prepared by the method described above.

[0023] Compared with the prior art, this application has the following advantages: The application proposes that by forming a highly uniform and stable micro-nano bubble system in concrete, the air-entraining agent can significantly improve the concrete's resistance to freeze-thaw cycles, mechanical strength, and durability. At the same time, its preparation process is mild and environmentally friendly. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] This application provides a preferred embodiment of the preparation process for a high-performance cross-linked cationic concrete air-entraining agent, as follows: Step 1: Under nitrogen protection, add 2-5 parts of polyamine compound groups and 10-12 parts of bromoalkane to 40-50 parts of tetrahydrofuran and reflux for 2-4 days. Transfer the solution to a four-necked flask, maintain a stirring speed of 150-250 rpm, add 1-2 parts of sodium citrate solution and 5-8 parts of emulsifier, sonicate to disperse, heat to 60℃-80℃, and stir continuously for 1-2 hours to form a homogeneous pre-emulsion.

[0026] Step 2: Place 20-25 parts of the pre-emulsion in a photoreactor, add 15-20 parts of hydrophilic polyoxyethylene ether, 1-2 parts of initiator, and 10-15 parts of phosphate modifier. Purge with nitrogen for 30 minutes to remove oxygen, and react under 365nm ultraviolet light for 3-5 hours. The reaction temperature is controlled at 25±2℃ and maintained at a constant temperature using a circulating water bath.

[0027] Step 3: After the reaction is complete, transfer the solution to a rotary evaporator flask, then add 10-15 parts of micro / nano bubble solution, 8-10 parts of pretreated nanocellulose suspension, and 1-5 parts of foam stabilizer. Continue stirring for 30-50 minutes, then remove unreacted monomers using a rotary evaporator at 40℃-60℃ under reduced pressure. Filter the final product through a 0.22μm microporous membrane to obtain a high-performance cross-linked cationic concrete air-entraining agent.

[0028] The preparation of the pretreated nanocellulose suspension involves mixing 10-15 parts of nanocellulose with 100-150 parts of ethanol solution, adding 1-3 parts of silane coupling agent, stirring at room temperature for 2-4 hours, centrifuging and filtering to separate the suspension, and washing with ethanol to remove unreacted coupling agent.

[0029] Regarding the selection of raw materials: The polyamine compound has one or more of the following groups: N-(3-aminopropyl)-1,3-propanediamine, N,N'-methylenebisacrylamide, 1,1,4,7,10,10-hexamethyltriethylenetetramine, N,N,N′,N′-tetramethylethylenediamine, and 1,1,4,7,7-pentamethyldiethylenetriamine. The bromoalkane has one or more of the following groups: 1-bromooctadecane, 1-bromopentadecane, 1,14-dibromotetradecane, 1-bromotetradecane, and 1-bromododecane. The emulsifier has one or more of the following groups: sodium stearate, sodium dodecyl sulfate, benzalkonium chloride, and polysorbate-80. The hydrophilic polyoxyethylene ether has one or more of the following groups: polyoxyethylene oleyl alcohol ether, polyoxyethylene lauryl alcohol ether, polyoxyethylene fatty alcohol ether, and polyoxyethylene alkylphenol ether. The initiator has one or more of the following groups: azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, dodecyl peroxide, potassium persulfate, and ammonium persulfate. The phosphate ester modifier is one or more of triisopropylphenyl phosphate, phosphate acrylate, tris(2,4-di-tert-butylphenyl) phosphate, 2-(m-tolyloxy)ethyl phosphate, and hydroxyethyl methacrylate phosphate. The foam stabilizer is one or more of dodecyl dimethylamine oxide, alkanolamide, polyethylene glycol, polyvinylpyrrolidone, and coconut oil diethanolamide. The silane coupling agent is one or more of γ-(methacryloyloxy)propyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, octadecyl dimethyltrimethoxysilylpropylammonium chloride, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and bis-(γ-triethoxysilylpropyl)tetrasulfide.

[0030] This application also provides the following embodiments: Example 1 The preparation process of high-performance cross-linked cationic concrete air-entraining agent is as follows: Step 1: Under nitrogen protection, 3 parts of 1,1,4,7,7-pentamethyldiethylenetriamine and 10 parts of 1,14-dibromotetradecane were added to 40 parts of tetrahydrofuran and refluxed for 3 days. The solution was then transferred to a four-necked flask, and while maintaining a stirring speed of 200 rpm, 1 part of sodium citrate solution and 5 parts of sodium dodecyl sulfate were added. The mixture was ultrasonically dispersed, heated to 60°C, and stirred continuously for 1.5 hours to form a homogeneous pre-emulsion.

[0031] Step 2: Place 20 parts of the pre-emulsion in a photoreactor, add 15 parts of polyoxyethylene fatty alcohol ether, 1.2 parts of benzoyl peroxide, and 10 parts of tris(2,4-di-tert-butylphenyl) phosphate, purge with nitrogen for 30 minutes to remove oxygen, and react under 365nm ultraviolet light for 3 hours. The reaction temperature is controlled at 25±2℃ and maintained at a constant temperature using a circulating water bath.

[0032] Step 3: After the reaction is complete, transfer the solution to a rotary evaporator flask, then add 12 parts of micro / nano bubble solution, 8 parts of pretreated nanocellulose suspension, and 2 parts of dodecyl dimethylamine oxide. Continue stirring for 30 minutes, then remove unreacted monomers under reduced pressure at 40°C using a rotary evaporator. The final product is filtered through a 0.22 μm microporous membrane to obtain a high-performance cross-linked cationic concrete air-entraining agent.

[0033] The preparation of the pretreated nanocellulose suspension involves mixing 12 parts of nanocellulose with 120 parts of ethanol solution, adding 1 part of γ-mercaptopropyltriethoxysilane, stirring at room temperature for 3 hours, centrifuging and filtering to separate the suspension, and washing with ethanol to remove unreacted coupling agent.

[0034] The concentration of the sodium citrate solution is 1%; A microbubble generation device was used to treat tap water to generate a micro / nanobubble solution with a bubble size distribution of 20 μm and a bubble concentration of 10. 8 per mL.

[0035] Example 2 The preparation process of high-performance cross-linked cationic concrete air-entraining agent is as follows: Step 1: Under nitrogen protection, add 2 parts of N-(3-aminopropyl)-1,3-propanediamine and 12 parts of 1-bromododecane to 45 parts of tetrahydrofuran and reflux for 2 days. Transfer the solution to a four-necked flask, maintain a stirring speed of 200 rpm, add 1 part of sodium citrate solution and 5 parts of polysorbate-80, sonicate to disperse, heat to 60°C, and stir continuously for 2 hours to form a homogeneous pre-emulsion.

[0036] Step 2: Place 20 parts of the pre-emulsion in a photoreactor, add 18 parts of polyoxyethylene alkylphenol ether, 1 part of potassium persulfate, and 10 parts of triisopropylphenyl phosphate. Purge with nitrogen for 30 minutes to remove oxygen, and react under 365nm ultraviolet light for 3 hours. The reaction temperature is controlled at 25±2℃ and maintained at a constant temperature using a circulating water bath.

[0037] Step 3: After the reaction is complete, transfer the solution to a rotary evaporator flask, then add 10 parts of micro / nano bubble solution, 10 parts of pretreated nanocellulose suspension, and 2 parts of alkanolamide. Continue stirring for 40 minutes, then remove unreacted monomers under reduced pressure at 40°C using a rotary evaporator. The final product is filtered through a 0.22 μm microporous membrane to obtain a high-performance cross-linked cationic concrete air-entraining agent.

[0038] The preparation of the pretreated nanocellulose suspension involves mixing 10 parts of nanocellulose with 110 parts of ethanol solution, adding 1 part of octadecyldimethyltrimethoxysilylpropylammonium chloride, stirring at room temperature for 3 hours, centrifuging and filtering to separate the suspension, and washing with ethanol to remove unreacted coupling agent.

[0039] The concentration of the sodium citrate solution is 1%; A microbubble generation device was used to treat tap water to generate a micro / nanobubble solution with a bubble size distribution of 20 μm and a bubble concentration of 10. 8 per mL.

[0040] Example 3 The preparation process of high-performance cross-linked cationic concrete air-entraining agent is as follows: Step 1: Under nitrogen protection, 5 parts of N,N,N′,N′-tetramethylethylenediamine and 12 parts of 1-bromopentadecane were added to 50 parts of tetrahydrofuran and refluxed for 4 days. The solution was then transferred to a four-necked flask, and while maintaining a stirring speed of 250 rpm, 2 parts of sodium citrate solution and 5 parts of sodium dodecyl sulfate were added. The mixture was then ultrasonically dispersed, heated to 80°C, and stirred continuously for 3 hours to form a homogeneous pre-emulsion.

[0041] Step 2: Place 25 parts of the pre-emulsion in a photoreactor, add 20 parts of polyoxyethylene lauryl ether, 2 parts of ammonium persulfate, and 12 parts of hydroxyethyl methacrylate phosphate. Purge with nitrogen for 30 minutes to remove oxygen, and react under 365nm ultraviolet light for 4 hours. The reaction temperature is controlled at 25±2℃ and maintained at a constant temperature using a circulating water bath.

[0042] Step 3: After the reaction is complete, transfer the solution to a rotary evaporator flask, then add 14 parts of micro / nano bubble solution, 10 parts of pretreated nanocellulose suspension, and 5 parts of coconut oil diethanolamide. Continue stirring for 50 minutes, then remove unreacted monomers under reduced pressure at 60°C using a rotary evaporator. The final product is filtered through a 0.22 μm microporous membrane to obtain a high-performance cross-linked cationic concrete air-entraining agent.

[0043] The preparation of the pretreated nanocellulose suspension involves mixing 15 parts of nanocellulose with 140 parts of ethanol solution, adding 2 parts of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, stirring at room temperature for 3 hours, centrifuging and filtering to separate the suspension, and washing with ethanol to remove unreacted coupling agent.

[0044] The concentration of the sodium citrate solution is 1.5%; A microbubble generation device was used to treat tap water to generate a micro / nanobubble solution with a bubble size distribution of 20 μm and a bubble concentration of 10. 8 per mL.

[0045] This application also provides the following comparative examples: I. Direct comparison with existing technologies / commercially available products (demonstrating superior overall performance) Comparative Example 1: Anionic air-entraining agent An anionic air-entraining agent, specifically sodium dodecyl sulfate (K12), was selected from the market. Parallel experiments were conducted under identical concrete mix proportions, curing conditions, and testing standards.

[0046] Comparative Example 2: Nonionic air-entraining agent A commercially available nonionic air-entraining agent, specifically Triton X-100 polyethylene glycol octylphenyl ether, was selected. Parallel experiments were conducted under identical concrete mix proportions, curing conditions, and testing standards.

[0047] II. Comparison of missing core components and replacement of key processes Comparative Example 3: Lack of emulsifier Compared with Example 1, no emulsifier was added in step one (an equal mass of tetrahydrofuran solvent was used instead), and the other components and processes were the same as in Example 1.

[0048] Comparative Example 4: Lack of phosphate ester modifier Compared with Example 1, no phosphate ester modifier was added in step 2, while the other components and processes were the same as in Example 1.

[0049] Comparative Example 5: Types of Phosphate Ester Modifiers to Replace Compared with Example 1, no phosphate modifier was added in step 2 (an equal mass of triethanolamine phosphate modifier was used instead), and the other components and processes were the same as in Example 1.

[0050] Comparative Example 6: Lacking cross-linking structure (no UV initiation step) Compared to Example 1, the UV-initiated crosslinking step in step two is omitted from the preparation process. After the pre-emulsion is formed in step one, it is directly mixed with hydrophilic polyoxyethylene ether, initiator, and phosphate ester modifier, and then step three is performed. Other components and processes are the same as in Example 1.

[0051] Comparative Example 7: Ordinary cellulose was used, without modification by silane coupling agents. Compared to Example 1, in preparing the pretreated suspension, only nanocellulose was dispersed in ethanol, without the addition of a silane coupling agent for modification. Other components and processes were the same as in Example 1.

[0052] Comparative Example 8: No foam stabilizer added Compared with Example 1, no foam stabilizer is added in step 3, while the other components and processes are the same as in Example 1.

[0053] Comparative Example 9: Micro / nano bubble solution omitted Compared to Example 1, no micro / nano bubble solution was added in step three (an equal mass of water solvent was used instead). Other components and processes were the same as in Example 1.

[0054] Performance testing of the products in the examples and comparative examples: The workability tests of hardened concrete were conducted on the air-entraining agent products prepared in the above examples and comparative examples, in accordance with the test methods for concrete mixture performance in the "Standard for Test Methods of Performance of Ordinary Concrete Mixtures" (GB / T 50080-2016). Specific concrete mix proportions are shown in Table 1, and the test results for cement and concrete performance are shown in Tables 2 and 3. Table 1 Concrete mix proportions (Kg / m³) 3 )

[0055] Table 2 Concrete Workability Test

[0056] Table 3. Concrete Strength and Durability Tests

[0057] The test results show that: The comparison results between Comparative Examples 1 and 2 and the Examples show that, compared with existing air-entraining agents, the air-entraining agent product prepared by the method provided in this application can effectively improve the flow and dispersion performance and air-entraining performance of concrete by introducing a large number of uniform, tiny, and stable air bubbles. At the same time, the appropriate amount of the air-entraining agent product of this application will not adversely affect the strength and durability of concrete.

[0058] The comparison results between Comparative Examples 3-9 and the Examples show that changing the core materials of the air-entraining agent preparation process, such as the type of emulsifier, phosphate ester modifier, and foam stabilizer, or omitting micro-nano bubbles, using ordinary cellulose, or not modifying the solution with silane coupling agent, will increase the diameter of the bubbles in the concrete prepared by the air-entraining agent, resulting in a slight decrease in the dispersion performance of the concrete, and a reduction in the strength and durability of the concrete.

[0059] In addition, the absence of core components of the air-entraining agent, such as the lack of phosphate ester modifier and cross-linking structure (no ultraviolet light initiation step), will result in a significant loss of concrete dispersion performance, a significant decrease in concrete compressive strength, and a significant adverse effect on carbonation performance, freeze-thaw resistance, and sulfate attack resistance.

[0060] This application should include at least the following design concept, mechanism of action, and beneficial effects: Design concept: 1. This application introduces a cross-linked cationic structure and a phosphate modifier. This air-entraining agent forms a uniform and stable micro-nano bubble system in concrete, which effectively alleviates internal stress concentration, significantly inhibits crack propagation, thereby greatly enhancing the freeze-thaw cycle resistance of concrete, extending the service life of the structure, and significantly improving the durability and freeze-thaw resistance of concrete.

[0061] 2. Through the synergistic effect of cross-linked cationic networks and hydrophilic polyoxyethylene ethers, the fluidity and cohesiveness of cement paste are improved, and bleeding is reduced. At the same time, the introduction of nanocellulose and silane coupling agents strengthens the aggregate-paste interface bonding, thereby improving the compressive strength and overall mechanical properties of concrete.

[0062] 3. By using a combination of foam stabilizer and micro / nano bubble solution, combined with the interface regulation effect of phosphate ester modifier, a highly stable foam system is formed, ensuring that bubbles are evenly distributed and remain stable during the concrete hardening process, effectively improving the accuracy of air content control, and making it suitable for harsh construction environments.

[0063] 4. By designing photoresponsive crosslinking monomers, precise crosslinking of air-entraining agent molecules is achieved under mild conditions, significantly improving the uniformity and stability of bubbles. Simultaneously, the use of green components such as silane coupling agents-modified nanocellulose enhances the utilization rate of solid waste resources, effectively solving the failure problem of traditional air-entraining agents under complex working conditions. Furthermore, the utilization of solid waste-derived raw materials reduces the environmental footprint, aligning with the development trend of green building materials.

[0064] Beneficial effects: 1. Freeze-thaw resistance and durability: This application introduces a cross-linked cationic network structure and a phosphate modifier to form a highly uniform and mechanically stable micro-nano bubble system in concrete. This system can effectively buffer the internal stress generated by freeze-thaw cycles and inhibit the generation and propagation of microcracks, thereby significantly improving the freeze-thaw resistance and long-term durability of concrete.

[0065] 2. Enhanced Mechanical Properties and Workability: Cationic groups generate strong electrostatic adsorption with negatively charged components in the cement paste, while hydrophilic polyoxyethylene ether segments provide steric hindrance and lubrication. These two factors synergistically significantly improve the fluidity and cohesiveness of the concrete, reducing bleeding and segregation. Simultaneously, silane coupling agent-modified nanocellulose strengthens the paste-aggregate interface, enhancing the overall mechanical strength of the concrete.

[0066] 3. Bubble Stability and Adaptability: A highly efficient bubble stabilizing system is constructed by combining a foam stabilizer with a micro / nano bubble solution and integrating the interfacial regulation function of a phosphate ester modifier. This system ensures that bubbles remain uniformly distributed and dimensionally stable throughout the entire process of concrete mixing, transportation, pouring, and hardening, and maintains excellent performance even under harsh environments such as low pressure and high salinity / alkali.

[0067] 4. Green and environmentally friendly preparation process: The preparation process uses ultraviolet light to initiate cross-linking, with mild reaction conditions (near room temperature) and low energy consumption, avoiding the safety and equipment problems caused by high temperature and high pressure. The raw materials selected include biomass-derived components such as nanocellulose, which are solid waste-derived components. Therefore, this application improves resource utilization and conforms to the concepts of green chemistry and sustainable development.

[0068] Finally, it should be noted that: The specific parameters or some commonly used reagents or raw materials in the above embodiments are specific embodiments or preferred embodiments under the concept of this application, and are not intended to limit them; those skilled in the art can make adaptive adjustments within the concept and protection scope of this application.

[0069] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing a high-performance cross-linked cationic concrete air-entraining agent, characterized in that, Includes the following steps: S1. Under an inert atmosphere, polyamine compounds and bromoalkanes are refluxed in an organic solvent. The resulting reaction solution is then mixed with an emulsifier and sodium citrate solution, dispersed, and then heated to emulsify, resulting in a homogeneous pre-emulsion. S2. The pre-emulsion is mixed with hydrophilic polyoxyethylene ether, initiator and phosphate ester modifier. Under deoxygenation and temperature control conditions, ultraviolet light is used to initiate the polymerization and cross-linking reaction of the system to obtain the intermediate product. S3. The intermediate product is mixed and stirred with the micro / nano bubble solution, pretreated nanocellulose and foam stabilizer, and then the volatile unreacted monomer components are removed by vacuum distillation. Finally, the mixture is filtered to obtain the air-entraining agent. The pretreated nanocellulose is obtained by modifying nanocellulose with a silane coupling agent.

2. The preparation method according to claim 1, characterized in that: S1. Under an inert atmosphere, polyamine compounds and bromoalkanes are refluxed in an organic solvent at 60-70°C for 2-4 days. The resulting reaction solution is then mixed with an emulsifier and sodium citrate solution. After ultrasonic dispersion, the mixture is heated to 60-80°C and stirred for 1-3 hours to emulsify, resulting in a homogeneous pre-emulsion. The reactant components, by weight, include: 2-5 parts of polyamine compound, 10-12 parts of bromoalkanes, 40-50 parts of organic solvent, 1-2 parts of sodium citrate solution, and 5-8 parts of emulsifier.

3. The preparation method according to claim 1 or 2, characterized in that, The polyamine compound is one or more of N-(3-aminopropyl)-1,3-propanediamine, N,N'-methylenebisacrylamide, 1,1,4,7,10,10-hexamethyltriethylenetetramine, N,N,N',N'-tetramethylethylenediamine, and 1,1,4,7,7-pentamethyldiethylenetriamine. The bromoalkane is one or more selected from 1-bromooctadecane, 1-bromopentadecane, 1,14-dibromotetradecane, 1-bromotetradecane, and 1-bromododecane; The emulsifier is one or more of sodium stearate, sodium dodecyl sulfate, benzalkonium chloride, and polysorbate-80; The organic solvent is tetrahydrofuran; The concentration of the sodium citrate solution is 1%–2%.

4. The preparation method according to claim 1, characterized in that, S2. Take a portion of the pre-emulsion and mix it with hydrophilic polyoxyethylene ether, initiator and phosphate ester modifier. Remove oxygen from the reaction environment by passing an inert gas through the mixture and control the temperature of the reaction system at 23-27℃. Irradiate the mixture with ultraviolet light at a wavelength of 365nm for 3-5 hours under constant temperature conditions to obtain the intermediate product. The reaction raw material components of S2, by weight, include: 20-25 parts of pre-emulsion, 15-20 parts of hydrophilic polyoxyethylene ether, 1-2 parts of initiator, and 10-15 parts of phosphate ester modifier. S3. Add the micro / nano bubble solution, the pretreated nanocellulose suspension and the foam stabilizer to the intermediate product and stir to mix evenly. Then remove the volatile unreacted monomer components by rotary evaporation under reduced pressure at 40℃-60℃. Finally, filter to obtain the air-entraining agent. The reaction raw material components of S3, by weight, include: 10-15 parts of micro-nano bubble solution, 8-10 parts of pretreated nanocellulose suspension, and 1-5 parts of foam stabilizer.

5. The preparation method according to claim 1, characterized in that, In step S3, the stirring and mixing time is 30-50 minutes; the filtration is performed using a microporous membrane with a pore size of 0.22 μm.

6. The preparation method according to claim 1, characterized in that: The hydrophilic polyoxyethylene ether is one or more of polyoxyethylene oleyl alcohol ether, polyoxyethylene lauryl alcohol ether, polyoxyethylene fatty alcohol ether, and polyoxyethylene alkylphenol ether; The initiator is one or more of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, dodecyl peroxide, potassium persulfate, and ammonium persulfate; The phosphate modifier is one or more of the following: triisopropylphenyl phosphate, phosphate acrylate, tris(2,4-di-tert-butylphenyl) phosphate, potassium 2-(m-tolyloxy)ethyl phosphate, and hydroxyethyl methacrylate phosphate. The foam stabilizer is one or more of the following: dodecyl dimethylamine oxide, alkanolamide, polyethylene glycol, polyvinylpyrrolidone, and coconut oil diethanolamide.

7. The preparation method according to claim 1, characterized in that: A microbubble generation device was used to treat water to generate a micro / nanobubble solution, wherein the bubble size distribution was 0.1 μm-50 μm and the bubble concentration was 10. 7 cells / mL–10 8 cells / mL; The pretreated nanocellulose was obtained by surface modification reaction of nanocellulose with silane coupling agent in alcohol solution, followed by solid-liquid separation and washing.

8. The preparation method according to claim 1, characterized in that: The preparation process of the pretreated nanocellulose suspension is as follows: The nanocellulose was mixed evenly with an alcohol solution, then a silane coupling agent was added. The mixture was stirred at room temperature for 2-4 hours, centrifuged and filtered to separate the nanocellulose, and washed with an alcohol solution to remove unreacted coupling agent. The raw material components, by weight, include: 10-15 parts of nanocellulose, 100-150 parts of alcohol solution, and 1-3 parts of silane coupling agent.

9. The preparation method according to claim 7 or 8, characterized in that: The silane coupling agent is one or more of γ-(methacryloyloxy)propyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, octadecyldimethyltrimethoxysilylpropylammonium chloride, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and bis-(γ-triethoxysilylpropyl)tetrasulfide; The alcohol solution is an ethanol solution.

10. A high-performance cross-linked cationic concrete air-entraining agent, characterized in that, It is prepared by the preparation method described in any one of claims 1-9.

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